Process for the hydrocracking of hydrocarbon oils under reaction conditions so as toretain substantial amounts of aromatics in the naphtha product



United States Patent Ofiice 3,354,076 Patented Nov. 21, 1907 This invention relates to an improved hydrocracking process'and in particular tothe hydrocracking of furnace aoilsto gasoline.

Hydrocracking'to form gasoline,, as.practiced commercially at the present time, produces :a total naphtha product which has only a moderate octane number. The octane number of this naphtha-istoo low for regular gasoline.

Therefore, the largest part ofvthis fraction must.be=furv.ther upgraded by catalytic reforming. The low octane "number of the-total naphtha product is due to'the fact that hydrogenation of the 'aromatics present in the feed stock .occurs simultaneously with the hydrocracking reaction. While-some degree: ofhydrogenation is desirable to facilitate hydrocracking, conventional hydrocracking processes ,oversaturate the feed stockbecause of the combination ;of temperatures,. pressures and space velocities used in these processes. Since there is an excessvof hydrogenation, the-naphthenes inthe naphtha product must be dehydrogenated by catalytic reforminglin order toincrease the octane number of the product and to recover the hydrogen used in the saturative{hydrocracking step. This additional step of catalytic reforming increases the overallcost of producing gasoline from furnace oils. This cost may be increased even further where catalytic reforming capacity is not available and an additional processing unit must be added to the hydrocracking complex.

Attempts to eliminate the problem of oversaturation of the hydrocracked product have in some cases involved the use of a catalyst with a low metal content (less than one-half the normal metal content).-In general, however, such catalysts are also less activefor hydrocracking and,

as a result, a higher temperature or-a lower space velocity must beused forthe same degree of hydrocracking-conversionHIn, addition, the rate of deactivationof this type The use of a higher temperature would also increase the rate of deactivation and together with thepreviously mentioned higher rate of, deactivation of the=.-le ss active In accordance ,with our invention, We hydlsocrackga petroleum fraction which boils above about 400F., which contains a substantial amount of aromatic hydrocarbons and which is substantially free of nitrogen and I asphaltic materials. The aforementioned feed stock is by- .xdroc racked at a temperature.betwccnabout 700 and'900" F., at a hydrogen partial pressure; between 531301112 1500 and 4000 psig and at a space velocity ;not lower than -.that given by the formula LHSV=2.0+0.001'1? 0.02A -where P=hydrogen partial pressure in p.s.i.-g. and

A=aromatic content of the feed in percent by volume.

Operation in accordance with our invention provides a gasoline or naphtha fraction, particularly a 180 to 400 P. fraction, which has retained a major proportion of the aromatic constituents present in the charge stock and whichhas a relatively high octane number. The advantage of obtaining such a-product fraction can be twofold. First, the necessity of reforming *the" hydrocracked product inorder-to obtain asufliciently high'octane num- .of catalyst has generally been greater, undoubtedly asa result of :less hydrogenation of coke-forming materials.

.catalyst, -would considerably shorten thelength of the' on-stream period between catalyst regeneration.

her fraction is eliminated. Second, .the avoidance of oversaturation, as evidenced by aromatics retention, reduces the amount of hydrogen consumed in the hydrocracking thereby eifecting an economy of operation.

The catalyst used in our process may beany hydrocracking catalyst which comprises a hydrogenating component composited-with an acidic siliceous cracking catalyst. Preferred catalysts are oxides, or sulfides of one or-more metalsfrom Group VI, left-hand column, and/ or Group VIII-composited with an active siliceous cracking component. The major portion of the catalyst is the porous refractory support having a-high cracking activity. This support may advantageously be any siliceous cracking support such as any of the conventional siliceous cracking catalystsgThe support may be a synthetic silicaalumina cracking catalyst such as a conventional high silica, low aluminasynthetic cracking catalyst. Generally speaking, the support can have an SiO content inthe range of 50 to and an Al o vcontent in.the range of 50m 10%. Preferred specific catalysts for this-process includethe oxides and/ or sulfides of nickel, cobalt, tungsten, ,silver, Zinc, palladium, platinum, or combinations of theseon a silica-alumina acidicsupport as described above. The catalyst can also be promoted by the addition of a halogen :such .as fluorine or chlorine in amounts of between 1% and 1.0%. Alternatively such a halide may be added to the feed stock. The catalyst used in this hydrocracking, process; can be regenerated by combustion in :the usual fashion. -Such regeneration will'result in elimination of harmful compounds such as nitrogen compounds and the poisoningefiect thereof. It alsoremoves carbonaceous deposits which lower-the activity of the catalysts.

The invention is applicable to hydrocracking treatment of any hydrocarbon containing a substantial amount of hydrocarbon components boiling above 400 R, which hydrocarbon (l) issubstantially free of .asphaltic materials, 2) is. substantially free of nitrogenous impurities and (3) contains a substantial amount of aromatic hyv.drocarbons. Thus, the invention is applicable to the hydrocracking of cracked or straight run petroleum fractions such as heavy naphtha, kerosene, furnace oil, gas

oil, deasphalted residuum, and distillate shale oils which otherwise meet the above requirements. The invention isv especially applicable to the hydrocracking of highly aromatic stocks such as solvent extracts or catalytically --cracked cycleoils, particularly those boiling in the furnace .oilrange from about 400 .to about 650 F. Thefeed stockshould contain less than about 20 ppm. nitrogen and it is-preferable thatitcontain less-than 5 or 10 ppm. nitrogen and even less thanl 'p.p.m. nitrogen. This low nitrogen feed stock can be prepared by pretreatment in a prehydrogenation stage. Ho Wev er, the nitrogen removal procedure ,maybe anydesired type which will lower the compounds may be removed in known manner byadsorpl tion using adsorbents such asactivated alumina, silica ge], etc. Alternatively, nitrogen compounds may be removed in known manner by treatment with aqueous acidic solutions suchasaqueous sulfuric acid. However, we pre- -fer .to utilizeamoderate pressure hydrogenation process for .the removal of the-nitrogen compounds.

nitrogen content to the-,desired value. Thus, the nitrogen During the course of removing the nitrogenous impurities vfrornthe feed .stock .by preliminary catalytic hydrogenation,.aconsiderable amount .of sulfur is also removed from the feed stock. In such cases and also when the feed is already free-of sulfur, -it has been found advantageous, but not necessary, to add certain amounts of sulfur backto the feed stocks in the hydrocracking stage,

and for this reason a sulfur compound, such as hydrogen sulfide, butyl mercaptan, thiophene, carbon disulfide, etc., may be mixed with'the hydrogen used to hydrocrack the 7 3 feed stock or with the feed stock. The amount of sulfur added can vary from 50 to 10,000 p.p.m. and preferably between about 300 and 3000 p.p.m. In the event that a 1 sulfur compound is neither added nor present, the catalyst may be sulfided prior to use for hydrocracking.

The feed stock to the hydrocracking step should contain more than about aromatic compounds by volume and preferably more than about 50% aromatic compounds. The use of a highly aromatic feed stock results in a naphtha product or higher aromatic content and, as a result, a higher octane number. Also, hydrocracking a feed stock which is high in aromatics produces a naphtha product which does not require catalytic reforming. If a feed stock containing less than 30% aromatics is used, a substantial portion of the product may require reforming although it will still be higher in aromatic content and octane number than a similar product derived from conventional hydrocracking of the same feed stock.

about 700 to about 800 F., are employed during the earlier periods of operation and, as the catalyst becomes gradually deactivated throughout the run, the temperature is increased to a maximum of about 800 to about 900 F. in order to maintain a more or less constant level of hydrocracking. Advantageously, a temperature in the range from about 720 to about 780 F. is maintained during the initial period of operation and the run is terminated when a temperature in the range from about 820 to about 870 F. is reached.

The pressure range (hydrogen partial pressure) for our hydrocracking process is between about 1500 and 4000 p.s.i., preferably between about 1700 and 3000 p.s.i. We have found that a pressure in this range, but in excess of 1700 p.s.i.g., is advantageous to minimize catalyst deactivation. Although the extent of hydrogenation of aromatics is generally increased by increase in pressure, we have found that even pressures in the higher portion of the pressure range employed by us, when used in combination with temperatures and space velocities in the ranges employed in our invention do not result in excessive hydrogenation of the aromatics present.

Since one of the objects of this invention is the effective retention of aromatics, the space velocity is of critical importance. It is desired to obtain a final hydrocracked product having as high an aromatic content as possible and, therefore, operating conditions are selected so as to retain a substantial level of aromatics, that is so that the 180 to 400 F. naphtha fraction has an aromatic content of at least about 60% that of the feed. For effective retention of aromatics, the liquid hourly space velocity must be greater than 2.0 in all instances. The minimum space velocity which can be employed in a particular hydrocracking operation in accordance with our invention is determined mainly by the hydrogen partial pressure employed and the aromatic content of the feed stock. This minimum value can be calculated from the equation LHSV=2.0+0.001P-0.02A where P is hydrogen partial pressure expressed as p.s.i.g. and A is aromatic content of the feed expressed as percent by volume. At a particular hydrogen partial pressure with a particular aromatic content feed stock space velocities higher than indicated by the above equation can be satisfactorily employed in 'our invention. Advantageously, space velocities ranging from 1.1 to 2.5 times the minimum value provided by the equation are employed. We have found that, although space velocities in the range from greater than 2.0 to about 20.0 are satisfactory, in most situations the preferred range of space velocities will vary from about 3.0 to about 8.0 volumes of feed per volume of catalyst per hour.

In this process the temperature is not an independent variable but is adjusted in conjunction with the hydrogen partial pressure and space velocity to maintain the desired degree of hydrocracking as measured by conversion. Conversion is defined as 100 percent minus percent by volume of the total feed not converted to products boiling below the initial boiling point of the feed. In the practice of our invention conversion is maintained in the range from about 40 to about 75%, preferably from about to about Conversions below about 40% have been found to be economically undesirable, while conversions above about effect too high a degree of hydrogenation and saturation of desired aromatics and also result in an undesirably high rate of catalyst deactivation.

We have found that the process of our invention can be conducted employing a hydrogen feed rate in the range of about 2000 to 40,000 standard cubic feet of hydrogen per barrel of feed stock (s.c.f./bbl.) and preferably from about 5000 to about 15,000 s.c.f./bbl. The hydrogen purity during hydrocracking need only be about 50% or slightly above although higher purity, such as, for example, abou to is usually preferred.

We have also found that the process of our invention can be conducted with a recycle operation wherein the unconverted 400 F.+ residue from the hydrocracking effluent is returned as part of the charge to the hydrocracking step. Surprisingly, the yields obtained from the recycled fraction are not substantially diminished in any way over the yields obtained when treating the fresh feed. Thus, the conversion, rate of catalyst deactivation, aromatics content of the product and the octane rating of the product are substantially the same whether treating the fresh feed or the recycle fraction.

In order to illustrate our invention in greater detail reference is made to the following examples.

EXAMPLE I An FCC furnace oil obtained as a by-product of catalytic cracking was pretreated in a hydrogenation step to remove nitrogen to a level of less than 1 p.p.m. This pretreated feed had the inspections shown in Table I. The pretreated feed was then hydrocracked under the condi tions of this invention. The reaction conditions used in this run and the results obtained are given in the first column of Table III. This same pretreated feed was also hydrocracked under reaction conditions conventionally used for the hydrocracking of a low nitrogen feed stock. The reaction conditions used in this run and the results obtained are given in the second column of Table III. In a third run a high nitrogen FCC furnace oil having the inspections shown in Table II was hydrocracked under reaction conditions conventionally used to hydrocrack high nitrogen feed stocks. The reaction conditions and the results obtained are given in column three of Table III. The catalyst used in each of these runs had the same composition. It was a presulfided nickel-tungsten catalyst composited with a silica-alumina cracking base, (6% Nil9% W2% F).

7 End Point: n 609 also reflected in the lowerhydrogen consumptionlt will be noted from a comparison of columns 1 and 3fthat the present'invention has advantages over conventional high temperature-high nitrogen hydrocracking. Thus; the higher level of hydrocrackingthe' higher retention of aromaticsland the higher octanenumber for the 180".- 400. F."ffraction show superiorityfor the instant invention. It will also be noted that the composition and octane number as well as the proportion of aromat'icsretained in the .18-400 F. naphthaproduct obtained in this. run

employing a high' n'itrogen feed (column '3) is substantially the same as that provided in the conventionaloperation :(column 2) as distinguished from the results obtained iu accordance with 'our invention (column 1).

Table II n 7 EXAMPLE vII M gg i In this example another pretreated FCC furnace oil i i y Y having the inspections indicated in 'Table 'IV below was v X5. 9:. ype (Percent y W 61 4 subjected to hydrocracking employing both the operating 7 conditions required byour invention as "well as conven- S E tional hydrocracking conditions used for a stock having a um es alow nitrogen'content'feed. Nitrogen: ppm. 360 Su'lfur: percent by wt. 0.98 Table IV DiStillati0n,-ASTM-D158: v v API 27 Over Point: F 386 Nitrogen; 0.7 462 Sulfur: p. p.m. 44 524 Hydrocarbon type '(percent 'by VOL): 90% 604 Aromatics 57.6 End Pomt: F. 650 ol fi 2 I Saturates 41.2 Table :IIl Distillation, D86

. Over point: F 381 1 2 3- 5% at: F. 415 10 425 Gonven- Gonven- IPresetnt vtional ggqnall 3.0 4.5.6

nven 1on I ow 1g Temp. Temp Tem erature, F 750 60 7 50 571 Press ilre,p.s.i.g 1,750 1,200 1,750 End-point: .F. 621 @paf; Velocityt, goL/hlnlvfolfinnu 6. 0 1. 5 2.0

ei dfiii q 'alntHaiti- 0.4' 0.1 0.6 'catalysterffpleyedm} nt w ill-19% Propane- 4.9- 3. 2 8 W2% F on TripleA Sll'lCa-alllmllZta 'WhlCh had been f% 5;; ,prereduced :with hydrogen at600 'F. and 1750 p.s.i,g.:for 18 2-400 2 23-? one hour. The operating conditions-employedineach of n if gei'dinstiaigtng these two runs together withinspection data for the prods. c.f./bbl, 30 1,020 2.010 ucts obtainedis shown 1n Table V below. II1S8eCf%l;lSF-)Ilght Gasoline f 7 ravit jinrr s3 1 83.1 81 1 ,Table V Octane Number Research, l N ;3c(c. T GF 99 99.6 99.4 a 1; a d'SO 'lOO hir vn gmrr 43.3 :7 44 5 ififij fifiiifi Hydrocarbon Type, percent Processby-VoL:

.foflinatics e i O eration Conditions: .1 animus j 7 8 40 l Space Veloeity, vol./hr;/vol 1 3 ,0 t ,g phg Temperature, ..F 667 785 alle 11111 91's! 5 H dro enPartialPressure, 1,065 1,750 Research, +3cc. TEL/-Gal-. 94.7 86.5 86.5 g fiasawpercenltby 62 Motor, TEL/Gal 80:8 Gas Charge Rate, s.c.f./b.bl 9,130 9, 30

Recycle GasHydrogen' Content, pe i s 7 78 It-should be: noted from the datain Table llI that conm f gi fb $ggfiffig g; '1 version'to-products boiling below 400 F. was-abont=72% Gr i.(pereentrbywt.)-'. 0.2' 0.4 t I Propane .4.;6 9.6 -to 75%. 1n the first two'runs. A comparison of'columns 15:1 18,1 1 and 2 of Table -III shows that-thequality of the.prodightasol n 28. 7 29.2 uctsformed' under'the conditions of our invention -(colgft figif gt i ffii; *umn 1 is substantially =better than when employing a y og n p b h ns from conventional) 275 MW nltrogen feed stock and low temperature, :pressure Plcoduct Inspections, Light Gas line; Grav. -andspacevelocity as in theprior=art hydrocracking procigg g z ess. (columnlp). Thns,-the octanenumber of the naphtha -Res earch,-+ 3c :-.TEL 7 ('180.-400 F.) obtainednn accordance withour invengfg l g-ggg-b'ggg 193-2 tion is higher than that obtained from conventional 1 55 Gravity, API 47.8 44.1 temperature hydrocracking. The octane number of the fi 137861907? 334 339 p v ydrocal'oon Type naphtha is higher because of its higher aromatics content Ammams 216 3,9 as discussed previously. The total cyclics are-ab0ut the g i g ggg 3 31 -3 same in both cases confirming that the difference isa o n mfl 'rf result of lesser extent of saturation at the reaction con- 0 52-2 39-3 ditions of this invention. This difference in saturation is l From the above "data it will be noticed, first of all, that the hydrogen .consurnption required in the run illustrating 5 our invention'was'about 275 s.c.f./bbl. less than that required with the conventional process. Furthermore, it will be noted that in, the naphtha fraction of the product obtained in accordance with-our invention the aromatic content was "almost double that obtained when treating the 70 "same 'charge stockbut under conventional"conditions. It

will also be noted that the naphtha-product-of our invention had a research octane number (+3 cc. TEL) of 96.9, while the naphtha fraction obtained in accordance with .the conventionafprocess had a corresponding octane numboth hydrocrackingsteps was a 6% Ni19% N aphtha Aromatics, percent by vol.

EXAMPLE In In this example a sample of the same feed stock employed in Example II was subjected .to hydrocracking in accordance with our invention and the unconverted porv of 6.0 and a hydrogen feed rate of 10,000 s.c.f./bbl. The

conversion and rate of catalyst deactivation for both of these hydrocracking steps together with product inspections are shown in Table VI below.

Table VI Pretreated FCC Furnace Oil (Original Feed) Unconverted 400 F.+Fraction From Single- Pass Operatron Feed Stock Conversion, percent by vol. at 50 hrs 86 86 Initial Rate of Deactivation, percent Conversion per 24 hrs Aromatic Content of Feed, percent by vol.

Inspections of Products, 180-400 F Octane Number:

Research, +300. TEL/gal Motor, +3cc. TEL/gal 400 F.+Aromatics, percent by vol- It will be noticed from the above data that both the conversion and rate of catalyst deactivation were the same for both the original feed and the unconverted fraction. Furthermore, it will be noted that the aromatic content of the 180400 F. naphtha products are almost identical for both the freshfeed and unconverted fraction. Similarly, the research octane number of both product fractions are almost identical. Finally, it will be noticed that the 400 F.+ material from the second hydrocracking stage, which employed as charge the unconverted fraction from the first stage, has an aromatics content of about 42%, thus indicating that, although some saturation undoubtedly occurs in each hydrocracking step, most of the aromatics are still retained.

EXAMPLE IV In order to illustrate the eifects of temperature and pressure in hydrocracking operations conducted in accordance Temperature, F Pressure, p.s.i.g.:

7 API 32.2 0.8

Gravity: Nitrogen: p.p.m. Sulfur: p.p.m.

8 Hydrocarbon type (percent by vol.):

Aromatics 38.5 Olefins 3.4 Saturates 58.1

Distillation, D86:

Over point: F 420 5% at: F. 464 10 474 30 500 50 530 558 592 End point: F. 614

In all of the hydrocracking runs of this example, the catalyst employed was a prereduced 6% Ni19% W 2% F on Triple A" silica-alumina. A space velocity of 6.0 and a hydrogen feed rate of 10,000 s.c.f./-bbl. was also employed in each of the runs.

In the first series of runs the temperature employed was 750 F. and the hydrogen partial pressure was varied in the range from 1500 to 2500 p.s.i.g. The conversions obtained for each of these pressures is shown in Table VIII below.

TABLE VIII Hydrogen Partial Conversion,

Pressure, p.s.i.g. percent by Vol.

From the data in Table VIII it can quite clearly be seen that when operating at the above indicated conditions, it is necessary to employ a hydrogen partial pressure of at least 1500 p.s.i.g. in order to obtain the minimum desired conversion of about 40%. Furthermore, it will be seen that increasing the hydrogen partial pressure through the range up to about 2500 p.s.i.g. is effective to increase conversion up to 60% by volume. These data clearly indicate that a hydrogen partial pressure of 1500 p.s.i.g. is obviously not an optimum and while these data do not demonstate that an optimum does exist it is quite evident that if such optimum hydrogen partial pressure does exist it must be substantially greater than 1500 p.s.i.g.

In another series of hydrocracking runs the temperature employed was varied from 750 to 850 F. while the hydrogen partial pressure was varied from 1500 to 2500 p.s.i.g. The aromatics content and research octane number of the 180-400 F. product naphtha fraction as well as conversions obtained are shown in Table IX below.

TABLE IX Aromatic Content of Naphtha Conversions, Percent olume Research, +300. TEL Octane Numb by V or of Naphtha.

a series of hydrocracking operations employing varying From the data in Table IX it will be seen that increasing the hydrogen partial pressure from 1500 p.s.i.g. to 2500 p.s.i.g. has substantially no detrimental effect on either the 0 aromatics content or the octane number of the 180- 400 F. naphtha product. Furthermore, the data in Table 1X clearly indicate that increasing the temperature to above 750 F. is effective to increase both the aromatics content and the octane number of the product naphtha 12 75 fraction. The conversions obtained with this series of runs also indicate the same trend as shown by the conversions obtained in the first series. of runs of this example.

EXAMPLE V In this example the feed stock employed in Example H is subjected to hydrocrackin'g in two separate runs employing the conditions of our invention including a temperature of about 750 F., a hydrogen partial pressure of about 1750 p.s.i.g., a liquid hourly space velocity of about 6 and a hydrogen feed rate of about 10,000 s.c.f./bbl. In one of these runs the catalyst is a 6% Ni19% W2% F on silica-alumina such as described in the previous examples. The fluorine is combined with the other ingredients of this catalyst by impregnation during catalyst preparation. In the other run the catalyst employed is a 6% Ni19% W on silica-alumina without any combined halogen. During the first 88 hours of operation of the run employing the catalyst prepared without halogen, fluorine in the form of o-fluorotoluene is added to the feed at a rate of 50 p.p.m. of fluorine.

After conducting both of these runs for a period of 10 days, the following data are obtained. In the run in which fluorine is added to the feed a conversion of about 70% by volume is obtained and the 180400 F. product fraction contains about 43% by volume aromatics and has an octane number, Research +3 cc. TEL, of about 96. On the other hand the run employing the catalyst containing combined fluorine and no halogen addition a conversion of only 64% by volume is obtained and the l80-400 F. product fraction contains about 42% by volume aromatics and has an octane number, Research +3 cc. TEL, of about 96.

It is also interesting to note that although the quantity of fluorine added to the feed is sufiicient, if combined with the catalyst, to provide a catalyst containing 2.1% by weight fluorine, the fluorine content of such catalyst at the end of the 10 day period of operation is only 1.7% by weight, while the catalyst originally containing about 2% by weight fluorine had a fluorine content of 1.9% by weight.

We claim:

1. The process for hydrocracking a petroleum fraction which boils above about 400 R, which is substantially free of asphaltic material, which contains a substantial amount of aromatic hydrocarbons and which contains less than about 20 p.p.m. of nitrogenous impurities to produce substantial mounts of hydrocarbons boiling in the gasoline range with concomitant high retention of aromatics, which process comprises contacting said hydrocarbon feed stock with hydrogen in the presence of a hydrogenating catalyst composited with an acidic siliceous cracking catalyst, at a hydrogen partial pressure of between about 1500 and 4000 p.s.i. and at a minimum liquid hourly space velocity given by the formula LHSV=2.0+ 0.001P0.02A, where P=hydrogen partial pressure in p.s.i.g. and A=aromatic content of the feed in percent by volume, at a temperature of between about 700 and 900 F., said conditions of temperature, pressure and space velocity being adjusted to maintain a conversion level of from about 40% to 75% during the on-stream reaction whereby a hydrocracked 180-400 F. naphtha product which contains aromatic hydrocarbons in an amount at least approximately 60% that of the feed is obtained.

2. The process of claim 1 wherein the petroleum fraction contains at least about 30% by volume aromatics.

3. The process of claim 1 wherein the petroleum fraction contains at least about 50% by volume aromatics.

4. The process of claim 1 wherein the petroleum fraction contains less than about 10 p.p.m. of nitrogen.

5. The process of claim 1 wherein the petroleum fraction contains less than 1 p.p.m. of nitrogen.

6. The process of claim 1 wherein the hydrogen partial pressure is from about 1700 to about 3000 p.s.i.g.

7. The process of claim 1 wherein the temperature is from about 720 to about 870 F.

ployed duri g heinitial t n-stream period is from about 700 to 800 F., the temperature is gradually increased during the on-stream. period to maintain conversion and theprocess is terminated when a temperature in the range from about 800 to 900 F. is reached. 7 9.The process of claim '8 wherein the initial temperature is from about 720 to about 780 F. and "the terminal temperature is from about 820 to about 870 F.

10. The process of claim 1 wherein the liquid hourly space velocity is from about 2 to about 20.

11. The process of claim 1 wherein the space velocity is from about 1.1 to 2.5 times the minimum value given by the formula LHSV=2.0+0.001P0.02A.

12. The process of claim 1 wherein the liquid hourly space velocity is from about 3.0 to about 8.0.

13. The process of claim 1 wherein the catalyst comprises a hydrogenating component selected from the group consisting of Group VI and Group VIII metals, their oxides and sulfides, composited with a major amount of an active silica-alumina cracking catalyst.

14. The process of claim 1 wherein the catalyst comprises nickel and tungsten composited with a major amount of an active silica-alumina cracking catalyst.

15. The process of claim 13 wherein the catalyst contains from about 1% to about 10% by weight of combined halogen.

16. The process of claim 13 wherein from about 2 to about 200 p.p.m. of halogen are added to the hydrocar' bon feed stock.

17. The process of claim 1 wherein the operating conditions of temperature, pressure and space velocity are adjusted to maintain a conversion from about 50 to about 60%.

18. The process of claim 1 wherein the unconverted portion from the hydrocracking eflluent boiling above about 400 F. is recycled to the hydrocracking.

19. The process for hydrocracking a furnace oil boiling from about 400 to about 650 R, which is substantially free of asphaltic material, which contains at least about 50% by volume of aromatic hydrocarbons and which contains less than about 1 p.p.m. of nitrogenous impurities to produce substantial amounts of hydrocarbons boiling in the gasoline range with concomitant high retention of aromatics which process comprises contacting the furnace oil feed stock with hydrogen in the presence of a catalyst comprising a hydrogenating component selected from the group consisting of Group VI and Group VIII metals, their oxides and sulfides, composited with a major amount of an active silica-alumina cracking catalyst at a hydrogen partial pressure from about 1700 to about 3000 p.s.i.g. at a temperature from about 720 to about 870 F. and at a liquid hourly space velocity from about 3.0 to about 8.0, said temperature, pressure and space velocity being adjusted to maintain a conversion to materials boiling below about 400 F. from about 50 to 60% during the on-stream reaction whereby a hydrocracked 180 to 400 F. product fraction which contains aromatic hydrocarbons in an amount at least 60% that of the feed stock is obtained.

20. The process for hydrocracking a petroleum fraction which boils above about 400 R, which is substantially free of asphaltic material, which contains at least about 30% by volume of aromatic hydrocarbons and which contains less than about 5 p.p.m. of nitrogenous impurities to produce substantial amounts of hydrocarbons boiling in the gasoline range with concomitant high retention of aromatics, which process comprises contacting said hydrocarbon feed stock with hydrogen in the presence of a hydrogenating catalyst composited with an acidic siliceous cracking catalyst, at a hydrogen partial pressure of between about 1500 and 4000 p.s.i.g. and at a minimum liquid hourly space velocity given by the formula LHSV=2.0+0.001P0.02A, where P=hydrogen partial pressure in p.s.i.g. and A=aromatic content of the v '11 i 12 .feed in percentby volume, the conditions of temperature, References Cited pressure and space velocity being adjusted to maintain UNIT D TA E ATENT a conversion level'of from about 40% to 75% during the E S T S P S naphtha product which contains aromatic hydrocarbo on-stream reaction whereby a hydrocracked 180-400 F.

ns 5 in an amount at least approximately 60% that of the feed DELBERT GANTZ Primary Exammer' is obtained. ABRAHAM RIMENS, Examiner.

3,213,012 A 10/1965 Kline et a1. 2 0 8-il1 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,354,076 November 21, 1967 Harold Beuther et a1.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 3, line 10, for "or" read of column 5, line 50, after "1" insert a closing parenthesis; column 9, line 46, for "mounts" read amounts line 52, for

"4000 p.s.i." read 4000 p.s.i.g.

Signed and sealed this 21st day of January 1969.

(SEAL) Attest:

EDWARD J. BRENNER Commissioner of Patents Edward M. Fletcher, Jr.

Attesting Officer 

1. THE PROCESS FOR HYDROCRACKING A PETROLEUM FRACTION WHICH BOILS ABOVE ABOUT 400*F., WHICH IS SUBSTANTIALLY FREE OF ASPHALTIC MATERIAL, WHICH CONTAINS A SUBSTANTIAL AMOUNT OF AROMATIC HYDROCARBONS AND WHICH CONTAINS LESS THAN ABOUT 20 P.P.M. OF NITROGENOUS IMPURITIES TO PRODUCE SUBSTANTIAL MOUNTS OF HYDROCARBONS BOILING IN THE GASOLINE RANGE WITH CONCOMITANT HIGH RETENTION OF AROMATICS, WHICH PROCESS COMPRISES CONTACTING SAID HYDROCARBON FEED STOCK WITH HYDROGEN IN THE PRESENCE OF A HYDROGENATING CATALYST COMPOSITED WITH AN ACIDIC SILICEOUS CRACKING CATALYST, AT A HYDROGEN PARTIAL PRESSURE OF BETWEEN ABOUT 1500 AND 4000 P.S.I. AND AT A MINIMUM LIQUID HOURLY SPACE VELOCITY GIVEN BY THE FORMULA LHSV=2.0+0.001P-0.02A, WHERE P=HYDROGEN PARTIAL PRESSURE IN P.S.I.G. AND A=AROMATIC CONTENT OF THE FEED IN PERCENT BY VOLUME, AT A TEMPERATURE OF BETWEEN ABOUT 700* AND 900*F., SAID CONDITIONS OF TEMPERATURE, PRESSURE AND SPACE VELOCITY BEING ADJUSTED TO MAINTAIN A CONVERSION LEVEL OF FROM ABOUT 40% TO 75% DURING THE ON-STREAM REACTION WHEREBY A HYDROCRACKED 180*-400*F. NAPHTHA PRODUCT WHICH CONTAINS AROMATIC HYDROCARBONS IN AMOUNT AT LEAST APPROXIMATELY 60% THAT OF THE FEED IS OBTAINED. 